Add retweet button component

Expand API service for retweet

src/components/retweet_button/retweet_button.js

@@ -0,0 +1,16 @@
+const RetweetButton = {
+  props: [ 'status' ],
+  methods: {
+    retweet () {
+    }
+  },
+  computed: {
+    classes () {
+      return {
+        'retweeted': this.status.repeated
+      }
+    }
+  }
+}
+
+export default RetweetButton